A developer supply container supplies developer to a developer receiving portion of a main assembly of an electrophotographic image forming apparatus. The container includes a developer accommodator, a discharge opening, a stirring member, a first receiver receiving a stirring member driving force from a first transmitter in the main assembly, a member opening and closing the opening, a second receiver receiving a force moving the openable member, and a second transmitter transmitting a force to the second receiver through a main assembly relay. By mounting the container to the main assembly, engagements are established between the first transmitter and the first receiver, between the second transmitter and the relay, and between the relay and the second receiver, so that a force is transmittable from the first transmitter to the first receiver, and a is transmittable from the second transmitter to the second receiver.